1. Field of the Invention
The present invention relates to a signal processing apparatus that includes gain setting means capable of variably setting, in particular, a Q value and that is suitable for sound field correction and to a signal processing method for use with the signal processing apparatus. Also, the present invention relates to a sound field correction system for performing correction of, in particular, frequency-amplitude characteristics.
2. Description of the Related Art
As one effector for changing frequency-amplitude characteristics (hereinafter simply referred to as “frequency characteristics”) of an audio signal, hitherto, a graphic equalizer (GEQ) is known. An example of a GEQ is one that is configured to include an operation element for instructing a gain at the center frequency of each frequency band for each equalizer element provided in such a manner as to correspond to each frequency band and that is configured to perform gain adjustment for each frequency band by a user manually operating the operation element.
As an equalizer element, furthermore, an equalizer element that is capable of variably setting the center frequency and the Q value (degree of sharpness) is also known as a so-called parametric equalizer (PEQ). That is, as a result of changing the center frequency and the Q value in the manner described above, the degree of sharpness of the shape of the frequency characteristics (gain window shape) and the position of the arrangement of the gain window in the direction of the frequency axis can be changed.
Here, whereas effectors for changing frequency-amplitude characteristics described above have become popular, in recent years, some car audio systems and AV (Audio Visual) systems for home use include an automatic sound field correction function for automatically performing various kinds of sound field correction by the system.
In such automatic sound field correction, for example, regarding frequency characteristics, a microphone is set in advance at a listening position, so that characteristics are measured on the basis of the result in which a test signal output from a speaker is detected by the microphone. Then, on the basis of the measurement result, signal processing is performed on an audio signal in such a manner that target frequency characteristics can be obtained. More specifically, the above-described equalizer is used to adjust the gain at each center frequency so that target frequency characteristics can be obtained.
As an example of the related art, Japanese Unexamined Patent Application Publication No. 1996-047079 can be cited.